Selectable frequency dielectric filter having a ganged relation output switch

Abstract

Coupling capacitors are connected between an input end and an output end, a resonator is connected between each of the coupling capacitor and the ground, and a capacitor and a switch are connected between one end of each resonator and the ground. When the capacitor is off, the frequency is set to the resonance frequency of the resonator, and when the switch is turned on, the capacitor is connected parallel to the resonator, so that the resonance frequency is shifted to a lower value, whereby a dielectric filter having multiple frequencies can be obtained.

What is claimed is: 
     
       1. A dielectric filter circuit having an input terminal and an output terminal, and formed of at least one dielectric resonator, said circuit comprising: a reactance element having one end connected to one end of said at least one dielectric resonator;   a selection switch for selectively connecting another end of said reactance element to another end of said at least one dielectric resonator for selecting a resonance frequency of said circuit; and   an output switch connected to said output terminal and related to said selection switch, for selectively distributing an output signal of said dielectric resonator when said resonance frequency is selected with said selection switch.   
     
     
       2. The dielectric filter circuit according to claim 1, wherein said reactance element includes a plurality of elements each having one end connected to one end of said at least one dielectric resonator, and   said selection switch includes a contact for selectively connecting another end of said plurality of elements to another end of said at least one dielectric resonator.   
     
     
       3. The dielectric filter circuit according to claim 2, wherein said plurality of elements comprise at least one capacitor. 
     
     
       4. The dielectric filter circuit according to claim 3, wherein said plurality of elements are capacitors. 
     
     
       5. The dielectric filter circuit according to claim 1, further comprising: an input switch connected to said input terminal and related to said selection switch and said output switch, for selectively switching an input signal applied to said dielectric resonator when said resonance frequency is selected with said selection switch and said output signal is selectively distributed with said output switch.   
     
     
       6. The dielectric filter circuit according to claim 1, wherein said reactance element is a capacitor. 
     
     
       7. The dielectric filter circuit according to claim 1, wherein said at least one dielectric resonator is a discrete dielectric resonator. 
     
     
       8. The dielectric filter circuit according to claim 1, wherein said at least one dielectric resonator is a block-type dielectric resonator. 
     
     
       9. The dielectric filter circuit according to claim 1, further comprising: an input switch connected to said input terminal and related to said selection switch, for selectively switching an input signal applied to said dielectric resonator when said resonance frequency is selected with said selection switch.   
     
     
       10. A dielectric filter circuit comprising: an input;   an output;   two coupling elements connected at a node and in series between said input and said output;   a dielectric resonator connected between said node and ground;   at least two reactance elements, each having one end connected to said note;   a selection switch for selectively connecting another end of said at least two reactance elements to ground for selecting a resonance frequency of said resonator; and   an output switch connected to said output and related to said selection switch, for selectively distributing an output signal of said dielectric resonator when said resonance frequency is selected with said selection switch.   
     
     
       11. The dielectric filter circuit according to claim 10, wherein said reactance elements are capacitors. 
     
     
       12. A dielectric filter circuit comprising: an input;   an output;   first, second and third coupling elements connected in series between said input and said output, said first and second coupling elements being connected at a first node, and said second and third coupling elements being connected at a second node;   a first dielectric resonator connected between said first node and ground;   a second dielectric resonator connected between said second node and ground;   first and second series circuits each having a selection switch and a reactance element connected between said first and second nodes and ground, respectively, for selecting resonance frequencies of said resonators; and   an output switch connected to said output and related to said selection switches, for selectively distributing an output signal of said dielectric resonators when said resonance frequencies are selected with said selection switches.   
     
     
       13. The dielectric filter circuit according to claim 12, further comprising: an input switch connected to said input and related to said selection switches and said output switch, for selectively switching an input signal applied to said dielectric resonators when said resonance frequencies are selected with said selection switches,and said output signal is selectively distributed with said output switch.   
     
     
       14. The dielectric filter circuit according to claim 12, further comprising: an input switch connected to said input and related to said selection switches, for selectively switching an input signal applied to said dielectric resonators when said resonance frequencies are selected with said selection switches.   
     
     
       15. The dielectric filter circuit according to claim 12, wherein said reactance elements are capacitors.